HbA1c for diagnosis and prognosis of gestational diabetes mellitus

Aims: HbA1c is a widely used marker in diagnosing type 2 diabetes mellitus (DM), but its clinical utility in diagnosing gestational diabetes mellitus (GDM) is not established. Here, we evaluated the clinical usefulness of HbA1c in diagnosing GDM and predicting the risk of future type 2 DM development among GDM patients. Methods: This retrospective, cross-sectional study included 321 subjects who underwent 100-g oral glucose tolerance tests (OGTT) during pregnancy. HbA1c and other variables were analyzed to evaluate their diagnostic performance for GDM. To evaluate the clinical usefulness of HbA1c in predicting future type 2 DM development, we classified GDM subjects who had more than 3 months of follow-up data into two subgroups: those who developed postpartum type 2 DM (PDM) and those who did not. Results: HbA1c was significantly higher in the GDM group than in the normal control group. With the 100-g OGTT as reference, HbA1c showed 91.3% sensitivity and 62% specificity at a cutoff value of 5.05% (32 mmol/mol) for GDM diagnosis. At a cut-off value of 5.25% (34 mmol/mol), sensitivity was 73.6% and specificity was 77.2%. HbA1c levels during pregnancy were higher in those with PDM than in those without PDM (5.91 [41 mmol/mol] vs. 5.44% [36 mmol/mol], p < 0.001). The prognostic value of HbA1c for PDM was evaluated by ROC curve analysis, with sensitivity of 78.6% and specificity of 72.5% at a cut-off value of 5.55% (37 mmol/mol). Conclusions: HbA1c showed high sensitivity with relatively low specificity for diagnosis of GDM in pregnant women and was a potential predictor of PDM. HbA1c may be able to be used as a simple and less invasive alternative screening test for OGTT in GDM patients. (C) 2015 Elsevier Ireland Ltd. All rights reserved.